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At least 19 recordsLinked to original sources
PubMed1988

In vitro and in vivo evaluation of C-20- and C-23-modified derivatives of tylosin against veterinary pathogens.

Three series of semi-synthetic derivatives of tylosin-related macrolides were evaluated for utility in veterinary medicine. 23-Modified derivatives of 5-O-mycaminosyltylonolide (OMT) possessed potent activity in vitro against species of Pasteurella and Mycoplasma. An experimental infection in chicks caused by Pasteurella multocida was utilized to evaluate efficacy; several of these derivatives of OMT effectively treated the infection when given subcutaneously, but none were effective after oral administration in drinking water. Macrolides retaining the 4'-O-mycarosyl moiety (tylosin, DMT) had relatively poor activity against Pasteurella in vitro. Certain 20-modified derivatives of desmycosin demonstrated good oral bioavailability in chicks and a lead compound with oral efficacy in the Pasteurella infection model was discovered.

Animals↗
PubMed1992

Restriction fragment length polymorphism and virulence pattern of the veterinary pathogen Escherichia coli O139:K82:H1.

Escherichia coli O139:K82:H1 strains originating from outbreaks and single cases of oedema disease in pigs were characterized by their genomic restriction fragment length polymorphism (RFLP), their virulence pattern, and by the occurrence as well as the genomic distribution of the determinants for hemolysin (hly) and verotoxins (shiga-like toxins; sltI, sltII). Whereas the RFLPs revealed considerable variation among the E. coli O139:K82:H1 isolates depending the origin and epidemic source of the strains, the virulence gene slt II was found to be present in nearly all strains in a particular chromosomal region. Similar to RFLPs, the plasmid profiles are useful for epidemiological analysis.

Animals↗
PubMed1990

In vitro susceptibility of selected veterinary bacterial pathogens to ciprofloxacin, enrofloxacin and norfloxacin.

The minimum inhibitory concentrations (MIC) of ciprofloxacin, enrofloxacin, and norfloxacin were tested for approximately ten clinical isolates of each of Actinobacillus pleuropneumoniae, Actinobacillus suis, Actinomyces pyogenes, Corynebacterium pseudotuberculosis, Erysipelothrix rhusiopathiae, Haemophilus parasuis, Haemophilus somnus, Pasteurella haemolytica, Pasteurella multocida, Rhodococcus equi, Streptococcus equi, Streptococcus suis and Streptococcus zooepidemicus. Ciprofloxacin and enrofloxacin had similar activity and were more active than norfloxacin. All isolates had an MIC of 1.0 microgram/mL or less for ciprofloxacin and enrofloxacin, and these drugs had particularly marked activity against the gram-negative bacteria tested.

Actinobacillus↗
PubMed1987

"Haemophilus somnus," a facultative intracellular pathogen of bovine mononuclear phagocytes.

We have reported previously that bovine neutrophils are unable to kill the bovine respiratory pathogen "Haemophilus somnus." In the present study we expanded our efforts and examined the interaction of bovine mononuclear phagocytes with this important veterinary pathogen. Bovine alveolar macrophages and blood monocytes ingested but did not kill opsonized "Haemophilus somnus" in vitro, whereas these same cells ingested and killed opsonized Escherichia coli. Because this suggested that "H. somnus" was a facultative intracellular pathogen, we developed an assay to monitor the intracellular fate of ingested "H. somnus" within bovine monocytes. Our results indicated that ingested "H. somnus" multiplied within bovine monocytes (1- to 2-log10 increase in 4 h); equivalent intracellular growth was noted for both a laboratory strain and a recent field isolate of "H. somnus." Bovine monocytes killed ingested E. coli (1- to 2-log10 decrease in 4 h) under the same assay conditions that were used to follow intracellular growth of "H. somnus," thus indicating that the assay conditions did not induce a generalized defect in monocyte antibacterial activity. Light and electron microscopic examination of "H. somnus"-infected monocytes confirmed that intracellular growth had occurred. We did not observe an obvious correlation between the release of superoxide anion from bovine mononuclear phagocytes that had ingested opsonized "H. somnus" and E. coli and the subsequent intracellular survival of the bacteria. The results of this study suggest that infected mononuclear phagocytes sustain "H. somnus" infections in cattle and thus contribute to the subacute to chronic clinical course that has been reported.

Animals↗
PubMed1979

[Parasitic adaptation phenomena of pathogenic fungi in human and veterinary medicine].

The pathogen species involved in medical and veterinary mycology can be divided into three categories according to their level of increasing adaptation to parasitism. Only the third category includes a few species (some dermatophytes) which can be regarded as genuine parasites. The opportunistic fungi belong to the first or the first two the third categories according to the given definition. The various possible factors of preadaptation or adaptation to parasitic life (physical factors, biochemical factors, avoidance of the immunological pressure and ecological factors) are discussed. Except for the species belonging to the first category the probably are efficient only if the host does not react normally.

Adaptation, Physiological↗
PubMed1991

Novel method for measuring growth of Treponema hyodysenteriae and its application for monitoring susceptibility of clinical isolates to antimicrobial agents.

A microdilution assay method was developed to determine MICs of antibiotics for Treponema hyodysenteriae and to estimate the bacterial burden of mice colonized by this swine pathogen. Hemolysis of bovine erythrocytes in broth was correlated with growth of the spirochete, and growth inhibition by drugs could be determined by measuring hemolysis. MICs of 10 antibiotics for eight clinical isolates of T. hyodysenteriae measured by this method were similar to values obtained by an agar dilution method and to values reported in the literature. This method was also used to demonstrate the elimination of T. hyodysenteriae from the ceca of infected mice following oral treatment with carbadox. The procedure described in this paper provides a rapid and simple method for determining MICs of antibiotics for T. hyodysenteriae and may be adapted for the purpose of determining the presence of this veterinary pathogen in cecal contents of experimentally infected mice.

Anaerobiosis↗
PubMed2025

Chromosomal genome assembly resolves drug resistance loci in the parasitic nematode Teladorsagia circumcincta.

The parasitic nematode Teladorsagia circumcincta is one of the most important pathogens of sheep and goats in temperate climates worldwide and can rapidly evolve resistance to drugs used to control it. To understand the genetics of drug resistance, we have generated a highly contiguous genome assembly for the UK T. circumcincta isolate, MTci2. Assembly using PacBio long-reads and Hi-C long-molecule scaffolding together with manual curation resulted in a 573 Mb assembly (N50 = 84 Mb, total scaffolds = 1,286) with five autosomal and one sex-linked chromosomal-scale scaffolds consistent with its karyotype. The genome resource was further improved via annotation of 22,948 genes, with manual curation of over 3,200 of these, resulting in a robust and near complete resource (96.3% complete protein BUSCOs) to support basic and applied research on this important veterinary pathogen. Genome-wide analyses of drug resistance, combining evidence from three distinct experiments, identified selection around known candidate genes for benzimidazole, levamisole and ivermectin resistance, as well as novel regions associated with ivermectin and moxidectin resistance. These insights into contemporary and historic genetic selection further emphasise the importance of contiguous genome assemblies in interpreting genome-wide genetic variation associated with drug resistance and identifying key loci to prioritise in developing diagnostic markers of anthelmintic resistance to support parasite control.

Animals↗
PubMed1992

Synthesis and structure-activity relationships of 7-diazabicycloalkylquinolones, including danofloxacin, a new quinolone antibacterial agent for veterinary medicine.

A series of novel 6-fluoro-7-diazabicycloalkylquinolonecarboxylic acids substituted with various C8 (H, F, Cl, N) and N1 (ethyl, cyclopropyl, vinyl, 2-fluoroethyl, 4-fluorophenyl, 2,4-difluorophenyl) substituents, as well as, 9-fluoro-10-diazabicycloalkylpyridobenzoxazinecarboxylic acids, were prepared and evaluated for antibacterial activity against a range of important veterinary pathogenic bacteria. The diazabicycloalkyl side chains investigated at the 7-position (benzoxazine 10-position) include (1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]heptane (2), (1S,4S)-2,5-diazabicyclo[2.2.1]heptane (3), (1R,4R)-5-methyl-2,5-diazabicyclo[2.2.1]heptane (4), 8-methyl-3,8-diazabicyclo[3.2.1]octane (5), 9-methyl-3,9-diazabicyclo[4.2.1]nonane (6), 1,4-diazabicyclo[3.2.2]nonane (7), 1,4-diazabicyclo[3.3.1]nonane (8), and 9-methyl-3,9-diazabicyclo[3.3.1]nonane (9). Among these side chains, in vitro potency was not highly variable; other properties therefore proved more critical to the selection of possible development candidates. However, the relative potencies observed for several of these compounds in mouse, swine, and cattle infection models correlated well with those seen in vitro. A combination of the N1 cyclopropyl group and the C7 (1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]hept-2-yl appendage conferred the best overall antibacterial, physiochemical, and pharmacodynamic properties. Hence, danofloxacin (Advocin, 2c) (originally CP-76,136, 1-cyclopropyl-6-fluoro-7-[(1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1] hept-2-yl]-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid) was selected as a candidate for development as a therapeutic antibacterial agent for veterinary medicine.

Actinobacillus Infections↗
PubMed1985

Rotavirus antigens.

The rotaviruses are important medical and veterinary pathogens that cause acute diarrheal disease in children and in the young of most mammalian and avian species. The successful development of a rotavirus vaccine should significantly reduce worldwide infant morbidity and mortality and economic losses and increase food-production. Recent successes in the cultivation and characterization of rotavirus strains from humans and animals have led to a better understanding of the major antigens of these viruses and the genes encoding these antigens. The products of three independent genes (1) the neutralization antigen (the outer capsid glycoprotein); (2) the subgroup antigen (the major inner capsid protein); and (3) the hemagglutinin (the outer capsid protease-sensitive protein) are the major viral antigens. The properties and structure of these antigens are discussed. Further knowledge should facilitate the synthesis and development of novel antigen or subunit vaccines.

Animals↗
PubMed1990

Complete sequence of the genomic RNA of O'nyong-nyong virus and its use in the construction of alphavirus phylogenetic trees.

The alphaviruses are a group of about 25 positive-strand RNA viruses that are important human and veterinary pathogens and that are geographically dispersed. We report here the complete nucleotide sequence of the genomic RNA of the alphavirus, O'nyong-nyong virus. The RNA is 11,835 nucleotides in length and the organization of the genome is typical of alphaviruses. Phylogenetic trees were constructed from the protein sequences of O'nyong-nyong and six other alphaviruses. Trees were constructed for each nonstructural and structural viral protein individually in order to detect any possible recombination events, as well as to examine the differential divergence among the various proteins. The members of each tree can be divided into three subgroups: the Semliki Forest virus subgroup (Semliki Forest, O'nyong-nyong, and Ross River viruses), the eastern equine encephalitis virus subgroup (eastern equine encephalitis and Venezuelan equine encephalitis viruses), and the Sindbis virus subgroup. Sindbis virus, which is geographically restricted to the Old World, is more closely related to the eastern equine encephalitis subgroup, which are New World viruses, than it is to the Semliki Forest virus subgroup, which are mostly Old World viruses. Western equine encephalitis virus is a special case because it is a recombinant virus. Its nonstructural and capsid proteins are most closely related to those of eastern equine encephalitis virus while its glycoproteins are most closely related to those of Sindbis virus. All members of a given subgroup have diverged the same amount from their common node point. However, the structural proteins of the Semliki Forest virus subgroup are more closely related to one another than those of the eastern equine encephalitis virus subgroup. This difference probably indicates that the members of the eastern equine encephalitis virus subgroup diverged earlier than the members of the Semliki Forest virus subgroup, which suggests that the alphaviruses originated in the New World.

Alphavirus↗
PubMed1992

The intestinal and serum humoral immune response of mice to orally administered antigens in liposomes: II. The response to liposome-entrapped bacterial proteins.

Effective oral adjuvants are needed to improve the intestinal immune responses to oral vaccines that are based on relatively low molecular weight antigens refined from veterinary pathogens. Liposomes prepared by different methods and composed of phospholipids of varying transition temperature were used to entrap cholera toxin (CT) and fed to mice. No significant increase in the intestinal antibody nor the serum IgA antibody response was detected but levels of serum IgG anti-CT antibody were significantly elevated in the group fed CT in phosphatidylcholine-based liposomes. Levels of antibody were significantly reduced in the groups fed CT in dipalmitoylphosphatidylcholine liposomes. Escherichia coli wall extract (ECWE) entrapped in certain liposome types and fed to mice elicited significantly increased serum anti-ECWE antibody responses but intestinal antibody responses were insignificantly different from the controls. These results suggest that orally administered liposomes fail to act as potent intestinal adjuvants for the entrapped antigens of bacterial origin used in this study.

Adjuvants, Immunologic↗
PubMed1990

Ehrlichiosis--a disease of animals and humans.

Ehrlichiae are one of several kinds of obligate intracellular bacteria. Taxonomically, they are grouped with rickettsiae, but they can be distinguished by their unique tropism for circulating leukocytes. Ehrlichia canis causes a pancytopenia in dogs that becomes chronic if untreated. Certain breeds develop severe infections, characterized by fever, anorexia, dramatic weight loss, marked pancytopenia, anemia, peripheral edema, and hemorrhage. Ehrlichia risticii, a recently discovered species, is the cause of a serious diarrheal disease of horses. Other species of ehrlichiae have been documented as being veterinary pathogens. Recent data indicate that E. canis or a closely related species causes an acute febrile illness in humans. Clinically, the disease is similar to Rocky Mountain spotted fever, except that most patients do not have a rash. Human ehrlichiosis appears to be tickborne and is prevalent primarily in the southern Atlantic and south-central states. A mild from of ehrlichiosis has also been documented.

Animals↗
PubMed1988

Retroviruses.

First brought to scientific attention as infectious cancer-causing agents nearly 80 years ago, retroviruses are popular in contemporary biology for many reasons. (i) The virus life cycle includes several events--in particular, reverse transcription of the viral RNA genome into DNA, orderly integration of viral DNA into host chromosomes, and utilization of host mechanisms for gene expression in response to viral signals--which are broadly informative about eukaryotic cells and viruses. (ii) Retroviral oncogenesis usually depends on transduction or insertional activation of cellular genes, and isolation of those genes has provided the scientific community with many of the molecular components now implicated in the control of normal growth and in human cancer. (iii) Retroviruses include many important veterinary pathogens and two recently discovered human pathogens, the causative agents of the acquired immunodeficiency syndrome (AIDS) and adult T cell leukemia/lymphoma. (iv) Retroviruses are genetic vectors in nature and can be modified to serve as genetic vectors for both experimental and therapeutic purposes. (v) Insertion of retroviral DNA into host chromosomes can be used to mark cell lineages and to make developmental mutants. Progress in these and other areas of retrovirus-related biology has been enormous during the past two decades, but many practical and theoretical problems remain to be solved.

Animals↗
PubMed1983

Detection of antigenically distinct rotaviruses from infants.

Antigenically distinct rotaviruses, i.e., viruses morphologically identical to conventional rotaviruses by electron microscopy, yet lacking the common group antigen(s) detected by an enzyme-linked immunosorbent assay, were found in 2 of 51 fecal samples from Bulgarian infants with rotavirus gastroenteritis. These antigenically distinct viruses contained 11 segments of double-stranded RNA, but they demonstrated a unique RNA migration profile after electrophoresis of the genome RNA in polyacrylamide gels. This report confirms the presence of a new group of rotaviruses in humans. The significance of these viruses is currently unknown, and specific diagnostic tests must be developed for epidemiological studies to determine their role as human and veterinary pathogens and to evaluate their impact on proposed vaccine development programs.

Antigens, Viral↗
PubMed2025

Probing orthobunyavirus reassortment using Bunyamwera and Batai viruses as models.

Reassortment is a critical evolutionary mechanism for segmented viruses, enabling the exchange of intact genome segments during co-infection and driving orthobunyavirus evolution; however, the molecular mechanisms underpinning this process remain unclear. With over 100 orthobunyavirus species, many of which are significant human and veterinary pathogens, understanding how reassortment influences transmissibility and virulence is essential for preempting the emergence of novel pathogens. Here, we use Bunyamwera virus (BUNV) and Batai virus (BATV) as models to explore orthobunyavirus reassortment through reverse genetics. We established the first reverse genetics system for BATV, generated reassortants, and employed minigenome assays to assess replication machinery compatibility. Additionally, we developed a novel hybridization chain reaction assay for high-resolution visualization of viral RNA segments. Our findings revealed that all six reassortants between BUNV and BATV are viable, exhibiting notable phenotypic differences in interferon-deficient (IFNAR-/-) mice. This work introduces essential tools and new insights into orthobunyavirus reassortment and pathogenesis, laying the groundwork for understanding this critical evolutionary process.

Animals↗
PubMed1991

Ehrlichiosis.

Ehrlichiae are tick-borne rickettsial organisms that are well known as veterinary pathogens. However, since 1986, over 100 cases of human infection by Ehrlichia canis or a closely related species have been identified primarily in the southeastern and south central United States. Human ehrlichiosis is characterized by high fever, rigors, headache, myalgia, anorexia, and, sometimes, gastrointestinal complaints. Rash occurs in a minority of cases. Commonly observed laboratory abnormalities include leukopenia, thrombocytopenia, anemia, and elevated hepatic aminotransferase levels. The illness is tick-borne and tetracycline or tetracycline analogs appear to be effective in treating the illness.

Animals↗